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I've been looking to pick up an older G11 for a few years, with the idea to mount it on a permanent pier in my yard. I'm moving to a new house with hopefully darker skies, so now was the time.

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Welcome to the club.? Not quite the full package Losmandy G11 mount close enough.??

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The best couplers to use here are a constant velocity type coupler that is designed to be used with some axial and angular misalignment.? Read up on the different types and you'll find that the best couplers where you may have some of both a double disc coupler is superior.? They take up some room and cost more but they are the best type for this job.? Where there is no angular misalignment just axial the Oldham's are also the top choice.??

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All other miniature couplers have issues that can be an issue if precision constant velocity power transmission is required.? Do some research and you'll see this is true.??

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To improve your classic 2-piece Losmandy worm drive backlash situation the best and simplist things to do are to hone the closed worm bearing block to allow the outer bearing to float in the block.? That's to say the bearing is allowed to move in and out slightly.? Fit a single R4 size Belleville spring disc inside the greased bearing carrier pointy end facing away from the bearing so the base of the spring disc pushes on the outer bearing shell.? Load a new worm bearing in the bearing carrier push it in and verify the besring moves back out.?

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The other tip is to tie the bearing blocks together in perfect bearing alignment with each other using the worm dust cover to hold the worm bearing blocks in place.? Essentially this gives you a one-piece worm block which allows you to effectively set backlash and keep the worm bearings aligned without having to struggle with dumb luck to get enough pressure on the bearing blocks while trying to set backlash.?

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The two bits above work together to solve one of the two biggest issues with worm drives.?

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If you are talking about the small undersized clutch spacer rings those are somewhat proof your G11 is an older production mount.? Older mounts seem to have come with these smaller diameter clutch spacers.? There is no cover for the clutch thrust bearing stack these spacers are a part of.? The thrust bearings on both axes just live somewhat exposed.? The good news is that they are easy to remove and easy to clean and relubricate.??

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If you would like there are clutch spacer replacements that match the body of the mount diameter available for about $20 a pair.? Largely cosmetic but they may help reduce the amount of dust and grit that can settle on the thrust bearings.? ?

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There should also be a black anodized cap on the back of the RA axis to keep dust and critters out of the RA axis.? I can't make out from the images if it is there.? It looks like the threaded retaining piece for the polar scope is there instead.? If you don't have the polar scope replace the polar scope retaining ring an replace it with the black machined alloy RA axis cap.? If you are missing the cap replacements are available fairly inexpensively.??

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Good luck on your adventure.??

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A quick and easy fix for the alignment of the two-piece worm blocks is to get a piece of AL angle iron (about 3/4 to 1 inch on a side and check it for flatness

on one exterior surface with a good straight edge).? Do the initial install and gently clamp the angle iron to one of the worm blocks and then apply a clamp the second

worm block to hold it to the flat section of the angle iron. Use soft jawed clamps if you have them.

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Do not tighten the screw (one each) that holds the worm block in position just yet. Just make snug them down but not so much that the

block can't slide when you apply a little force.

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Then nudge the worm into worm wheel to adjust the mesh and rotate the worm by hand thru a full rotation to find the high spot on the worm wheel.

The center of the worm wheel gear tooth pattern and the center of rotation of the axis are never quite perfect unless you spend many thousands.

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If it binds you'll be able to tell it by the force you need to exert with your fingers.

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Set the backlash at the high point of the worm/worm wheel contact and carefully?tighten the two screws.

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When you're happy, remove the two clamps and the angle iron.

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Why do I keep saying "snug", "gently", and "carefully"? It is because the metal of the worm bearing blocks is thin and if you get too aggressive about

tightening those screws down you run the risk of distorting the worm blocks and hence stressing the little bearings (which you might want to replace

in any case). I know all this because when I got my G11 used (about the same vintage) it had horrible Periodic Error. To solve it I replace the worms

with the brass high precision ones, replaced the bearing blocks, and installed new bearings. The prior owner had overtightened everything on the mount

and it was impossible for me to get the little worm bearings out of the blocks. Replacing the blocks and the bearings also made the install of the new

high precision worms easy.

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The only pricey part of this is the high precision (brass) worms.

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This isn't a high vibration operation, so there is no reason for us to get too enthusiastic with a wrench. Likewise, many get too aggressive about eliminating

backlash in an attempt to achieve perfection. Want perfection? Plan on paying 10X.

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I found there was no need to lap worms or anything.

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By the way, make sure you use something like SuperLube low temp grease. Avoid any grease with graphite: With moisture graphite can, I am told, pit aluminum

and that is what the worm wheel is made of.

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Mark Christensen